Develop scientigraphic procedures for quantitating the size of ischemic, infacrted, healing, and scarred myocardium, and will utilize animal and human subjects. Efforts will be directed toward validating the scientigraphic techniques utilizing Technetium (Tc-99m) pyrophosphate and Thallium (Thallium-201) and comparing these scientigrams to methods of tissue analysis. They propose to establish optimal imaging times after onset of myocardial infarction to set baseline data for assessing the effects of intervention in the clinical setting. A tissue culture study involving myocardial cells will be utilized to define the mechanism of the radionuclide lable uptake. Validation procedures or the imaging methodology include estimation of infarct size by planimetry of color photgraphs and polarographic measurement of myocardial oxygen tension and of hydrogen washout.